Table 1.

Summary of Problems, Impacts, and Solutions

Problem to Address	Potential Impact	Proposed Solution
Reliability of the residual apnea-hypopnea index
The residual apnea-hypopnea index, when measured over short periods of use, is a poor statistical estimator and may not be representative of the whole night.	The residual apnea-hypopnea index measured over short periods of use may not be reliable or may be biased.	Set a minimum device usage threshold (eg, > 1 h) for consideration of the residual apnea-hypopnea index.
Drift of the flow curve is due to large number of leaks.	Respiratory events cannot be detected, and the reported residual apnea-hypopnea index may be distorted.	Do not interpret residual apnea-hypopnea index in cases with excessive leaks.
Device replacement and absence of standardization
Transmission bugs can result from change in device model and/or manufacturer.	Data may not be transmitted, even though the patients use the device.	Missing values should not be replaced by zero values.
Parameters reported and summary statistics for leaks and residual apnea-hypopnea index are different among PAP manufacturers.	It is impossible to compare directly data from different devices.	Transition periods between two distinct devices require specific data preprocessing.
Multiple records of the same device for a patient
Several records can be sent on the same day.	Multiple rows exist for a patient with different values.	Aggregate multiple rows by summing the usage values and compute the mean weighted residual apnea-hypopnea index.
Mismatch occurs between the machine identification number and the patient identification number.	The records from two distinct devices are assigned to the same patient.	Provide the device identification number or remove the period with duplicate devices.
Dataflow issue exists.	Duplicate rows exist for a patient.	Remove duplicates.
Missing values
Transmission with external modem	Missing values because of connecting issues	Remove data recorded by PAP device with external modem.
Between two transmissions	Bias related to missing values	Missing values can be replaced by zero.
At the end of a patient’s sequence	Bias related to missing values	Imputation strategy should be defined.
Treatment interruption
With daily aggregated data, there is no distinction whether the patient did three 2-h naps or slept 6 h consecutively at night, for example.	The same aggregated value of CPAP adherence might reflect completely different CPAP usages that potentially are related to CPAP termination and prognosis (eg, insomnia)	Use raw data that provide the exact time of CPAP exposures during night and day.